ASTRO: Defining 'planet' wasRe: [extropy-chat] The list is not dead...

[Mike Lorrey]

In the interest of giving Damien's trash bin a break, I'd like to
restart the debate we had a year or two ago about the definition of
"planet". I believe it was back when Sedna or Quaoar was discovered
that the hew and froe began. 

At that time, I proposed, almost literally word for word, the
definition that Southwest Research Institute's Alan Stern is now
proposing: "A planet is a body that directly orbits a star, is large
enough to be round because of self gravity, and is not so large that it
triggers nuclear fusion in its interior."

NASA has also begged off, saying that it is not NASAs job to decide
what is or is not a planet, as it is the IAU's job.

If my, and Stern's, definition of a planet is accepted, as Stern seems
to think, Brown's discovery would become the 12 or 14th or so planet in
our solar system. Stern favors calling the smaller objects dwarf
planets, for example. Other astronomers prefer the term minor planet.
Another term bandied about is Kuiper Belt planets. Some don't like the
idea of applying the planet label at all. 

Caltech's Mike Brown, who discovered the most recent KBO, 2003 UB313,
which is about 1.5 times the mass of Pluto is calling for scientists to
give up using the term "planet" altogether, saying that it has become a
cultural, not a scientific, term. Brown was the first, in the 1990's,
to propose that Pluto be demoted from planet status, but with his most
recent announcement declared 2003 UB313 the "10th planet".

I myself would, beyond my and Sterns definition, divide planets up into
the following categories: gas giants, terrestrial planets, and ice
planets. I would regard the round asteroid Ceres as a terrestrial
planet (that it suffers from Jupiter's gravitational imperialism is a
separate issue), and all the KBOs that are round as ice planets.

Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
Founder, Constitution Park Foundation:
http://constitutionpark.blogspot.com
Personal/political blog: http://intlib.blogspot.com


		
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